Safety device for a punch press



p 1964 M. R. ATKINSON 3,147,836

SAFETY DEVICE FOR A PUNCH PRESS Filed Sept. 27, 1962 5 Sheets-Sheet 1Fl(5.l A.

INVENTOR MAURICE R. ATKINSON BWAW ATTORNEY Sept. 8, 1964 Y M. R.ATKINSON 3,147,836

SAFETY DEVICE FOR A PUNCH PRESS Filed Sept. 27, 1962 v s Sheets-Sheet, 2

INVENTOR MAURICE R. ATKINSON ATTORNEY Sept. 8, 1964 M. R. ATKINSON 7,8 6

SAFETY DEVICE FOR A PUNCH PRESS 5 Sheets-Sheet 5 Filed Sept. 27, 1962 8&W

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INVENTOR MAURICE R, ATKINSON ATTORNEY United States Patent 3,147,836SAFETY DEVICE FOR A PUNCH PRESS Maurice R. Atkinson, Streetsville,Ontario, Canada,

assignor to CTS of Canada, Ltd, Streetsville, 0ntario, Canada, acorporation of Canada Filed Sept. 27, 1962, Ser. No. 227,658 4 Claims.(Cl. 192129) This invention relates generally to safety devices forpunch presses and in particular to a mechanism which will ensure that apunch press will make only one stroke each time its clutch is engaged.

Single stroke mechanisms are used throughout industry in connection withpunch press operations. They are primarily installed for operatorprotection. Punch press operators get into a rhythm of loading andunloading the punch press dies and once their pattern of movements areestablished it is imperative that the punch press not make an additionalunexpected stroke for invariably it will occur when the operator has hishands under the press. Even where there is no concern for operatorsafety because the parts are mechanically loaded it is important to usesingle stroke mechanisms to prevent damage to the loading mechanismswhich would be under the die when the press makes its additional stroke.In addition to the above reasons, many of the tools and dies used inpunch presses are subject to damage when operated empty. These tools anddies are expensive to build but they are even more expensive to repairor replace.

There are many different types of single stroke mechanisms on the marketand in use today. It is the object of this invention to provide a singlestroke mechanism which employs a minimum of parts and which has anunusually high degree of reliability.

It is a further object of this invention to provide a single strokemechanism which will fail safe in that should it fail to operateproperly, the clutch on the press will not be engaged.

It is an additional object of this invention to provide a single strokemechanism which can be used either with a power operated press or a footor hand operated press.

The invention consists of a device which is installed between the powercylinder or the foot pedal of the press whichever may be the case andthe clutch pin disengaging mechanism. The device consists of areciprocally mounted pull rod which is attached to the foot pedal or thecylinder rod of the air cylinder and a reciprocally mounted latch rodwhich is attached to the retaining member of the clutch. The latch rodis provided with a latch on the end adjacent the end of the pull rod. Alatch dog is pivotally attached to the end of the pull rod and isdesigned to automatically engage the latch on the end of the latch rodwhen the pull rod is at the upper end of its stroke. A cam is providedin the housing and located so that the latch dog will be disengaged fromthe latch rod after the pull rod has moved the latch rod a suflicientdistance to engage the clutch of the press.

In operation the foot pedal is depressed or the air cylinder energizedand the pull rod moves downward pulling the latch rod with it. After ittravels a short distance the latch rod disengages the clutch retainingmeans of the press allowing the clutch to be engaged which starts thepress through its cycle. At this time the latch dog engages a cam in thehousing which releases the latch dog from the pull rod allowing it toreturn to its first position where it disengages the clutch of thepress. The length of travel and the time required for the draw bar toengage the clutch and then to be disengaged from the latch rod isarranged so that the clutch will be engaged only a sufficient length of3,147,836 Patented Sept. 8, 1964 disengaged from the latch rod, the drawbar continues downward to the end of its stroke. It then returns to itsoriginal position where the latch dog will automatically reengage thelatch bar preparatory to another cycle of operation.

By automatically releasing the latch rod from the remainder of themechanism, the foot pedal can be held down or the air cylinder can becontinuously energized yet the press will only perform one cycle ofoperation since the clutch cannot again be actuated until the draw baris allowed to return to the top of its stroke.

The invention will now be described in detail in connection with theattached drawings in which:

FIGURES 1 and 1A are drawings in elevation of a typical clutch for apunch press with the single stroke mechanism showed installed;

FIGURE 2 is a vertical cross sectional view of the single strokemechanism;

FIGURES 3 through 6 are schematic sectional views taken along line 33 ofFIGURE 2 illustrating the relative positions of the components of themechanism during one cycle of operation; and

FIGURE 7 is an enlarged sectional view of the latch dog engaging thedraw bar at the end of a cycle of operation.

The invention is illustrated in the drawings in connection with the pinclutch used with the majority of punch presses. The device would equallybe applicable to punch presses which use other types of clutches theonly requirement being that the controlled member must reciprocate froman engaging to a disengaging position. The invention lends itselfparticularly to the pin clutch type of press and therefore it will bedescribed in connection therewith.

These clutches are well known in the art and consist of three drive pins10 which are spaced apart and carried by the flywheel 9. Arranged toengage these flywheel drive pins is a clutch pin 11. The clutch pin inturn is held out of engagement with the drive pins by means of a latchblock 12. The latch block is tapered and is arranged so that when in theposition shown in FIGURE 1 it will either hold the clutch pin out ofengagement with the flywheel drive pins or it will engage the rotatingclutch pin and disengage it from the flywheel pins. In other words onceengaged the clutch pin can only make one revolution if the latch blockis returned to the position indicated before the flywheel completes onerevolution. One revolution is of course sutficient for one cycle of thepunch press and it is this principal that makes the use of a singlestroke mechanism possible.

The latch block is removed from its holding position against the clutchpin 11 by the linkage illustrated. The latch block 12 is carried by thearm 13 which is rotatably mounted to the press frame (not shown) by thepin 14. Attached to the arm 13 between the clutch pin and the pivot pinis the link 15 which is in turn pivotally mounted to the crank arm 16 bythe pin 17. The crank arm 16 is rotatably mounted to the frame of thepress by the pin 18. Attached to the end of the crank arm 16 by the pin2t) is the clutch rod 19 through the pin 20. The clutch rod 19 passesthrough a pair of springs 21 and 22 which combine with the bracket 23and the collars 24 attached to the rod to exert an upward force on therod 19 so that it will return the linkage to the clutch disengagingposition indicated when no downward force is being exerted on the rod.In other words when no force is being exerted on the clutch rod 19 theclutch will be disengaged. To engage the clutch the rod 19 must he moveddownward compressing the springs 21 and 22, rotating the crank arm 16 sothat the link 15 causes the arm 13 to rotate a sufiicient distancearound the pin 14 to remove the latch block from its holding positionadjacent the clutch pin 11.

This is a typical linkage arrangement used with this type of clutch andcan be actuated by either an air or hydraulic cylinder or a foot or handpedal. In FIGURE 1A an air cylinder is illustrated which is indicatedgenerally by the number 25.

The single stroke mechanism of the invention is indicated generally bythe number 27. It is installed between the piston rod 32 of the aircylinder and the clutch rod 19. The air cylinder is pivotally mounted tothe frame of the press by the bolt 26.

The single stroke mechanism of the invention consists of the housing 30which is rigidly attached to the air cylinder 25 by means of the bracket31. Reciprocally mounted in the housing and attached to the piston rod32 is the pull rod 33. The pull rod is made up of two identical members33a and 33b, which extend the length of the housing and which carry thelatch dog 34 between them by means of the pin 35. Reciprocally insertedbetween the two members of the pull rod is the latch rod 36 whichextends out of the upper end of the housing and is attached to the rod19 of the press operating mechanism by the pin 45. Extending through thehousing is the pin 37 which engages the slot 38 in the latch rod and theslot 45 in the pull rod to limit their travel in both directions. Alsomounted in the housing is the cam 39.

Operation The above description sets out the individual components ofthe single stroke mechanism. Now its operation will be described so thatthe inner relationship of all of these components can be fullyunderstood.

In FIGURES 3-7 a complete cycle of operation of the device isillustrated. In these views part of the housing 30 has been removedto'clearly show the relationship of the working parts. In FIGURE 3 themechanism is in the position of FIGURE 1 where the clutch is disengaged.

The operator then presses the control to operate the press. This allowsair under pressure to enter the air cylinder 25 and move the piston rod32, the pull rod 33, the latch dog 34, and the latch rod 36 downwardlyto the position shown in FIGURE 4. This movement is suificient to causethe latch block 12 to release the clutch pin 11 and engage the clutch.

It is at this instant as illustrated in FIGURE that the cam 39 begins toforce the latch dog to pivot on the pin 35 by which it is attached tothe pull rod and release the latch rod. In other words, the innerengaging surfaces 41 on the latch dog and 42 on the latch rod will beforced out of engagement with each other by the action of the cam 39thus releasing the latch dog from the pull rod. When this occurs thesprings 21 and 22 force the clutch rod and the latch rod back to theclutch disengaging position of FIGURE 1 while the pull rod continuesdownward. This condition is shown in FIGURE 6.

The air cylinder rod 32 will continue on downward until the pistonreaches the end of its stroke and will stay in this position until theair supply is reversed. If a foot pedal is being used in place of theair cylinder and as long as the foot pedal is depressed, the pull rodwill remain in the down position. The length of time that the aircylinder or the foot pedal is held in this position will have no effectwhatsoever on the operation of the press because it will have made justone cycle before the clutch was disengaged again by the latch block.

FIGURE 7 illustrates the position of the latch dog when the air cylinderis being returned to its original position. Just prior to the end of itsupper travel the cam surface 43 on the latch dog engages the end 44 ofthe latch bar which will in turn rotate the latch dog around the pin 35into position so that the surfaces 41 and 42 will be reengagedpreparatory to operating the press again.

As pointed out above the pin type clutch lends itself to this type ofmechanism very readily since it is so constructed that once the clutchpin has engaged the flywheel pins it will complete one cycle ofoperation before it can again be disengaged by the latch block. In thisway the action of the mechanism can be very rapid and the distancetraveled by the latch rod need only be sutficient to remove the latchblock an extremely short period of time after which it can be releasedand allowed to return to its disengaging position. In other words theaction of this mechanism is such that it will disengage the latch rodallowing it to return to its original disengaging position immediatelyafter the clutch pin has engaged one of the drive pins 10. In this waythere is no possibility of the press making more than one cycle ofoperation each time it is energized.

Another important feature of this invention is that if for some reasonthe latch dog should fail to engage the latch rod or if they shouldbecome inadvertently or prematurely disengaged before they reach thecam, the operator or the tools will not be placed in any danger sincethe malfunction will simply cause the press not to operate.

While there has been illustrated and described what is at presentconsidered to be a preferred embodiment of the present invention, itwill be appreciated that numerous changes and modifications are likelyto occur to those skilled in the art, and it is intended in the appendedclaims to cover all those changes and modifications which fall withinthe true spirit and scope of the present invention.

The invention claimed is:

1. In a safety device for a clutch operated punch press, the combinationof a housing, a pair of pull rods vertically disposed in spaced parallelrelationship in the housing and fixedly secured to each other, a latchdog pivotally mounted intermediate the pull rods and provided with a camsurface, an upwardly biased rod slidably mounted for limited movementintermediate the pull rods and having one end detachably connected tothe latch dog, the other end of the latch rod being connected to theclutch of the punch press, and a cam fixedly mounted in the housing fortripping the latch dog whereby upon moving the pair of pull rodsdownwardly the latch rod connected to the latch dog moves downwardlytherewith to engage the clutch of the press and upon further downwardmovement of the pull rods the cam trips the latch dog and releases thelatch rod to disengage the clutch.

2. In a safety device for a clutch operated punch press, the combinationof a housing, a pair of pull rods vertically disposed in spaced parallelrelationship in the housing and fixedly secured to each other, each ofthe pull rods being provided with an elongated slot, a pin fixedlymounted in the housing and havingits central portion disposed in theelongated slots for limiting movement of the pull rods with respect tothe housing, a latch dog pivotally mounted intermediate the pull rodsbelow the elongated slots and provided with a cam surface, an upwardlybiased latch rod having an elongated opening in alignment with theelongated slots provided in the pull rods and slidably mounted forlimited movement intermediate the pull rods, the adjacent ends of thelatch dog and the latch rod being detachably connected to each other, acam disposed in the housing for tripping the latch dog, and meansconnected to the pair of pull rods for moving the pull rods downwardlyto actuate the punch press whereby as the pull rods and the latch rodengaged to the latch dog are moved downwardly, the cam surface of thelatch dog engages the cam thereby pivoting the latch dog out ofengagement with the latch rod and causing the latch rod to slideupwardly a limited distance and disengage the clutch to halt operationof the punch press.

3. In a safety device for a clutch operated press, the

combination of a housing, a pair of vertically disposed pull rods inspaced parallel relationship mounted in the housing and fixedly securedto each other, an upwardly biased latch rod slideably mountedintermediate the upper portions of the pull rods, the upper end of thelatch rod being connected to the clutch of the press for engaging theclutch upon downward movement of the latch rod, means for limiting theslideable motion of the latch rod with respect to the pull rods and ofthe pull rods with respect to the housing, a latch dog pivotally mountedintermediate the pull rods having one end detachably connected to thelatch rod, and a cam mounted in the housing for tripping the latch dogwhereby upon moving the pull rods downwardly the latch rod detachablyengaged to the latch dog moves downwardly engaging the clutch foroperating the press and upon further downward movement of the pull rodsthe latch dog is pivoted out of engagement by the cam therebydisengaging the connection between the latch rod and the latch dogpermitting the latch rod to slide upwardly a limited distance anddisengage the clutch of the press while the pull rods are stilldownwardly disposed.

4. In a safety device for a punch press, the combination of a housing, apair of vertically slideable pull rods mounted in spaced parallelrelationship in the housing, a lost motion connection provided betweenthe housing and the pair of pull rods for limiting movementtherebetween, a latch dog pivotally mounted intermediate the pull rodsbelow the lost motion connection, a latch rod slideably and connected tothe lost motion connection for limiting the motion of the latch rod withrespect to the pull rods, the adjacent ends of the latch dog and thelatch rod each being provided with engaging shoulders, the other end ofthe latch rod being connected to a clutch rod of the punch press foroperatively controlling the clutch of the punch press, a cam fixedlymounted in the housing for tripping the latch dog, and means connectedto the pair of pull rods for moving the pull rods downwardly wherebyupon downward movement of the pull rods the latch rod detachably engagedto the latch dog moves downwardly for engaging the clutch of the punchpress and as the pull rods continue to move downwardly the latch dogengages the cam thereby pivoting the shoulder of the latch dog out ofengagement with the shoulder of the latch rod causing the latch rod toslide upwardly until limited by the lost motion connection and disengagethe clutch of the press.

References Cited in the file of this patent UNITED STATES PATENTS843,453 Hamann Feb. 5, 1907 920,726 Candu May 4, 1909 1,167,475 BenjaminJan. 11, 1916 1,988,103 Aliano Jan. 15, 1935 2,140,477 Minkel Dec. 13,1938 2,199,501 MacBlane May 7, 1940 2,328,524 Becker Aug. 31, 1943FOREIGN PATENTS 512,557 Germany Nov. 13, 1930

1. IN A SAFETY DEVICE FOR A CLUTCH OPERATED PUNCH PRESS, THE COMBINATIONOF A HOUSING, A PAIR OF PULL RODS VERTICALLY DISPOSED IN SPACED PARALLELRELATIONSHIP IN THE HOUSING AND FIXEDLY SECURED TO EACH OTHER, A LATCHDOG PIVOTALLY MOUNTED INTERMEDIATE THE PULL RODS AND PROVIDED WITH A CAMSURFACE, AN UPWARDLY BIASED ROD SLIDABLY MOUNTED FOR LIMITED MOVEMENTINTERMEDIATE THE PULL RODS AND HAVING ONE END DETACHABLY CONNECTED TOTHE LATCH DOG, THE OTHER END OF THE LATCH ROD BEING CONNECTED TO THECLUTCH OF THE PUNCH PRESS, AND A CAM FIXEDLY MOUNTED IN THE HOUSING FORTRIPPING THE LATCH DOG WHEREBY UPON MOVING THE PAIR OF PULL RODSDOWNWARDLY THE LATCH ROD CONNECTED TO THE LATCH DOG MOVES DOWNWARDLYTHEREWITH TO ENGAGE THE CLUTCH OF THE PRESS AND UPON FURTHER DOWNWARDMOVEMENT OF THE PULL RODS THE CAM TRIPS THE LATCH DOG AND RELEASES THELATCH ROD TO DISENGAGE THE CLUTCH.